Organic Speciation Sampling Artifacts

Abstract:

Sampling artifacts for molecular markers from organic speciation of particulate matter were investigated by analyzing forty-one samples collected in Philadelphia as a part of the Northeast Oxidant and Particulate Study (NEOPS). Samples were collected using a high volume sampler with two quartz fiber filters in series. Altogether thirty-one species including alkanes (C23-C31), hopanes (C27-C31), n-alkanoic acids (C10-C22), and aliphatic dicarboxylic acids (C3 to C9) were analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that species with low molecular weight or high vapor pressure had significant amounts of artifacts on the backup filters. Particulate organic species can be classified into the following three categories: 1) the amount collected on the backup filter was often a large fraction of the amount collected on the front filters (n-alkanes C23 and C24, n-carboxylic acids C10 to C14); 2) the amount collected on the backup filter was consistently a small fraction of the amount collected on the front filter (n-alkanes C25 to C28, hopanes C27 to C30, n-carboxylic acids C15 to C18, and dicarboxylic acids C3 to C9); 3) rarely observed on backup filters (n-alkanes C29 to C31, hopanes C31 and C32).

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